MICROSTRUCTURE, FLAW TOLERANCE, AND RELIABILITY OF CE-TZP AND Y-TZP CERAMICS

Ce-TZP and Y-TZP ceramics were heat-treated for various times and temperatures in order to vary the microstructure. Flaw tolerance was investigated using the indentation-strength test, Reliability was quantified using conventional two-parameter Weibull statistics, Some Ce-TZP specimens mere indented at slightly elevated temperatures where no transformation was observed, Results indicated that the Ce-TZP specimens were extremely ham tolerant, and showed a relatively high Weibull modulus that scaled with both R-curve behavior and ham tolerance, Y-TZP, on the other hand, with very little if any R-curve behavior or flaw tolerance, had a low Weibull modulus, The results also show that flaw history, i,e,, whether or not a transformation zone exists along the make of the crack, has a significant influence on strength, Strength was much less dependent on initial crack size when the crack had an associated transformation zone, whereas strength was highly dependent on cracks typical of natural processing defects, It is argued that the improvement in reliability, flaw tolerance, and dependence on ham history are all ramifications of pronounced R-curve behavior.